package company.jingji;

import java.util.Scanner;

/**
 * @author briarbear
 * @blog https://briarbear.github.io
 * @date 2018-09-20 14:48
 */
public class J2 {

    static String sortString(String str){
        String s = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        if (str==null || str.equals("")) return "";
        int[] array = new int[s.length()];
        char[] ch = str.toCharArray();

        StringBuilder res = new StringBuilder();

        for (int i = 0; i < ch.length; i++) {
            array[s.indexOf(ch[i])]++;
        }

        for (int i = array.length-1; i >= 0; i--) {
            if (array[i] == 0) continue;
            while (array[i] >0){
                res.append(s.charAt(i));
                array[i]--;
            }
        }

        return res.toString();

    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String res;

        String _str;
        try {
            _str = in.nextLine();
        } catch (Exception e) {
            _str = null;
        }

        res = sortString(_str);
        System.out.println(res);
    }
}
